1. Field of the Invention
The present invention relates to modulated electronic communications and more particularly to a system and method using Amplitude Shift Keying (ASK) modulation for such communications with an analog-emulating digital bandpass filter for demodulation and having application to infrared communication links.
2. Problem to be Solved
Amplitude Shift Keying (ASK) Modulation is one of the commonly used modulation methods for electronic communication. In communication systems using ASK encoding, demodulation is typically performed using an analog circuit while the controller which decodes the serial communication is designed using digital logic. The requirement for both analog and digital circuits tends to raise the cost of such communication systems. Furthermore, the analog bandpass filter used in the analog circuit usually requires many components, especially if it is to have a programmable cutoff frequency. In contrast, a digital bandpass filter lacks accuracy and still requires some minimal analog circuit to amplify the incoming signal. Although both types of filters have drawbacks, a system that requires various demodulators or different bandpass filters for multi-channel communication, will usually find a digital bandpass filter to be advantageous over an analog bandpass filter.
3. Objects
It is therefore an object of the present invention to provide an analog-emulating digital bandpass filter for use in demodulating ASK encoded signals.
It is another object of the present invention to provide an ASK MODEM including an improved digital bandpass filter for use in demodulating ASK modulated signals.
It is a further object of the present invention to provide an ASK MODEM including an improved digital bandpass filter for use in demodulating ASK modulated signals used in infrared (IR) communications.